This invention relates to the field of medical guidewires for advancing intraluminal devices such as stent delivery catheters, balloon dilatation catheters, atherectomy catheters and the like within body lumens.
The most common method for insertion of percutaneous catheters is the Seldinger technique. In this procedure, a local anesthesia is delivered and a skin puncture is made proximal to the femoral or brachial artery with an obturator positioned within a cannula (sheath). Once inside the artery, the obturator is removed and a guide catheter placed into the desired position in the anatomy through the cannula. Then a guidewire is inserted through the cannula into the artery. The guidewire is then advanced into the vasculature guided by fluoroscopic imaging to the desired site. Generally, the distal tip of the guidewire is pre-shaped by manufacture or has the ability to be shaped by the physician in order to steer the guidewire to the desired location by rotating and advancing in combination. Once the guidewire is at the desired treatment site, a diagnostic or therapeutic catheter is advanced over the guidewire, and the desired procedure is performed.
Further details of guidewires and devices associated therewith for various interventional procedures can be found in, for example, U.S. Pat. No. 4,748,986 (Morrison et al.); U.S. Pat. No. 4,538,622 (Samson et al.): U.S. Pat. No. 5,135,503 (Abrams); and U.S. Pat. No. 5,341,818 (Abrams et al.); which are hereby incorporated by reference in their entirety.
Because of the environment that guidewires are used in, and the purpose they serve, it is desirable to have several basic features for most, if not all, guidewires. The guidewire must navigate and advance within the lumens of a patient, coming into contact with delicate tissue. For this reason, the guidewire requires a soft, flexible distal tip which can be manipulated without causing injury to the vessel walls. Also, it must be sufficiently maneuverable to reach the required destination, which requires stable torsional characteristics, and a rigid proximal shaft that can be pushed to advance the guidewire. These characteristics are difficult to achieve, as one tends to negate the other. It is also desirable for the outer diameter of the guidewire to fit properly within the inside diameter of the lumen within which it is disposed. This can be problematic for guidewires designed for the peripheral arteries, such as those found within the legs and arms, because the size of the diagnostic and therapeutic devices used in these arteries are typically large, requiring a larger outer diameter guidewire, which can be stiffer and less flexible than coronary wires due to its size. In addition, because the guidewire is steered to the desired location within the vasculature under fluoroscopy, a radiopaque marker of some type is required, which is typically made from a precious metal coil, band or solder.
Conventional guidewires for angioplasty, stent delivery, atherectomy and other vascular procedures usually have an elongate core with one or more tapered sections near the distal end thereof and a flexible body such as a helical coil or a tubular body of polymeric material disposed about the distal portion of the core. A shapeable member, which may be the distal end of the core or a separate shapeable ribbon, is secured to the distal end of the core and extends through the flexible body, and is connected to the distal end of the flexible body by soldering, brazing, or welding, which forms a rounded distal tip. Torquing means are provided on the proximal end of the core to rotate, and thereby steer, the guidewire while it is being advanced through a patient's vascular system. The leading distal tip is highly flexible and atraumatic so it does not damage or perforate the vessel, and the portion behind the distal tip is increasingly stiff which better supports a balloon catheter or similar device.